jquery异步上传文件

一、创建input元素

 <input type="file" id="fileToUpload" name="fileToUpload" value="浏览"/>

二、导入jquery.js和ajaxfileupload.js文件

 jQuery.extend({


     createUploadIframe: function(id, uri)
     {
             //create frame
             var frameId = 'jUploadFrame' + id;
             var iframeHtml = '<iframe id="' + frameId + '" name="' + frameId + '" style="position:absolute; top:-9999px; left:-9999px"';
             if(window.ActiveXObject)
             {
                 if(typeof uri== 'boolean'){
                     iframeHtml += ' src="' + 'javascript:false' + '"';

                 }
                 else if(typeof uri== 'string'){
                     iframeHtml += ' src="' + uri + '"';

                 }
             }
             iframeHtml += ' />';
             jQuery(iframeHtml).appendTo(document.body);

             return jQuery('#' + frameId).get(0);
     },

     createUploadForm: function(id, fileElementId, data)
     {
         //create form
         var formId = 'jUploadForm' + id;
         var fileId = 'jUploadFile' + id;
         var form = jQuery('<form  action="" method="POST" name="' + formId + '" id="' + formId + '" enctype="multipart/form-data"></form>');
         if(data)
         {
             for(var i in data)
             {
                 jQuery('<input type="hidden" name="' + i + '" value="' + data[i] + '" />').appendTo(form);
             }
         }
         var oldElement = jQuery('#' + fileElementId);
         var newElement = jQuery(oldElement).clone();
         jQuery(oldElement).attr('id', fileId);
         jQuery(oldElement).before(newElement);
         jQuery(oldElement).appendTo(form);



         //set attributes
         jQuery(form).css('position', 'absolute');
         jQuery(form).css('top', '-1200px');
         jQuery(form).css('left', '-1200px');
         jQuery(form).appendTo('body');
         return form;
     },

     ajaxFileUpload: function(s) {
         // TODO introduce global settings, allowing the client to modify them for all requests, not only timeout
         s = jQuery.extend({}, jQuery.ajaxSettings, s);
         var id = new Date().getTime();
         var form = jQuery.createUploadForm(id, s.fileElementId, (typeof(s.data)=='undefined'?false:s.data));
         var io = jQuery.createUploadIframe(id, s.secureuri);
         var frameId = 'jUploadFrame' + id;
         var formId = 'jUploadForm' + id;
         // Watch for a new set of requests
         if ( s.global && ! jQuery.active++ )
         {
             jQuery.event.trigger( "ajaxStart" );
         }
         var requestDone = false;
         // Create the request object
         var xml = {};
         if ( s.global )
             jQuery.event.trigger("ajaxSend", [xml, s]);
         // Wait for a response to come back
         var uploadCallback = function(isTimeout)
         {
             var io = document.getElementById(frameId);
             try
             {
                 if(io.contentWindow)
                 {
                      xml.responseText = io.contentWindow.document.body?io.contentWindow.document.body.innerHTML:null;
                      xml.responseXML = io.contentWindow.document.XMLDocument?io.contentWindow.document.XMLDocument:io.contentWindow.document;

                 }else if(io.contentDocument)
                 {
                      xml.responseText = io.contentDocument.document.body?io.contentDocument.document.body.innerHTML:null;
                     xml.responseXML = io.contentDocument.document.XMLDocument?io.contentDocument.document.XMLDocument:io.contentDocument.document;
                 }
             }catch(e)
             {
                 jQuery.handleError(s, xml, null, e);
             }
             if ( xml || isTimeout == "timeout")
             {
                 requestDone = true;
                 var status;
                 try {
                     status = isTimeout != "timeout" ? "success" : "error";
                     // Make sure that the request was successful or notmodified
                     if ( status != "error" )
                     {
                         // process the data (runs the xml through httpData regardless of callback)
                         var data = jQuery.uploadHttpData( xml, s.dataType );
                         // If a local callback was specified, fire it and pass it the data
                         if ( s.success )
                             s.success( data, status );

                         // Fire the global callback
                         if( s.global )
                             jQuery.event.trigger( "ajaxSuccess", [xml, s] );
                     } else
                         jQuery.handleError(s, xml, status);
                 } catch(e)
                 {
                     status = "error";
                     jQuery.handleError(s, xml, status, e);
                 }

                 // The request was completed
                 if( s.global )
                     jQuery.event.trigger( "ajaxComplete", [xml, s] );

                 // Handle the global AJAX counter
                 if ( s.global && ! --jQuery.active )
                     jQuery.event.trigger( "ajaxStop" );

                 // Process result
                 if ( s.complete )
                     s.complete(xml, status);

                 jQuery(io).unbind();

                 setTimeout(function()
                                     {   try
                                         {
                                             jQuery(io).remove();
                                             jQuery(form).remove();

                                         } catch(e)
                                         {
                                             jQuery.handleError(s, xml, null, e);
                                         }

                                     }, 100);

                 xml = null;

             }
         };
 // Timeout checker
         if ( s.timeout > 0 )
         {
             setTimeout(function(){
                 // Check to see if the request is still happening
                 if( !requestDone ) uploadCallback( "timeout" );
             }, s.timeout);
         }
         try
         {

             var form = jQuery('#' + formId);
             jQuery(form).attr('action', s.url);
             jQuery(form).attr('method', 'POST');
             jQuery(form).attr('target', frameId);
             if(form.encoding)
             {
                 jQuery(form).attr('encoding', 'multipart/form-data');
             }
             else
             {
                 jQuery(form).attr('enctype', 'multipart/form-data');
             }
             jQuery(form).submit();

         } catch(e)
         {
             jQuery.handleError(s, xml, null, e);
         }

         jQuery('#' + frameId).load(uploadCallback   );
         return {abort: function () {}};

     },

     uploadHttpData: function( r, type ) {
         var data = !type;
         data = type == "xml" || data ? r.responseXML : r.responseText;
         // If the type is "script", eval it in global context
         if ( type == "script" )
             jQuery.globalEval( data );
         // Get the JavaScript object, if JSON is used.
         if ( type == "json" ) {
             if(data.indexOf('<pre') != -1) {
                 //此段代码时为了兼容火狐和chrome浏览器
 var newDiv = jQuery(document.createElement("div"));
                 newDiv.html(data);
                 data = $("pre:first", newDiv).html();
  }
             eval( "data = " + data );
         }
         // evaluate scripts within html
         if ( type == "html" )
             jQuery("<div>").html(data).evalScripts();
         return data;
     }
 });

注意：在ajaxfileupload中会用到jquery的handleError函数，但是此函数在1.4.2之后不存在了，所有如果用到更高的

版本需要复制进去

三、写调用代码

 function uploadImage() {
     $.ajaxFileUpload({
         url: 'photo/upload',//需要链接到服务器地址
         secureuri:false,
         fileElementId: 'fileToUpload',//文件选择框的id属性
         dataType:'json',//服务器返回的格式，可以是json
         success: function (data){
             if (data['result'] == 1) {

             }
         },
         error: function(data){
         }
     });
 }

四、写后台处理代码：

 List items = super.getUploadFileItems(req);//使用fileupolad组件获取request中的参数
                 HashMap<String, String> params = super.getUploadParams(items);
                 Iterator iter = items.iterator();
                 FileItem fileItem = null;
                 while (iter.hasNext()) {
                     FileItem item = (FileItem) iter.next();
                     if (!item.isFormField()) {
                         fileItem = item;
                         break;
                     }
                 }
                 byte[] imageContent = null;
                 String suffix = null;
                 if (fileItem != null) {
                     imageContent = IOTools.readContent(
                             fileItem.getInputStream(), 4096);
                     suffix = fileItem.getContentType();
                 }

注意：

（1）如果服务端想返回json格式，一定不能加上response.setContentType("application/json");

 否则IE和opera会解析成文件下载，或者写成response.setContentType("text/html");

结合strut2是result节点中也要设置contentType，否则浏览器总是提示将返回的JSON结果另存为文件，不会交给ajaxfileupload处理。

这是因为struts2 JSON Plugin默认的contentType为application/json，而ajaxfileupload则要求为text/html。

（2）返回url赋值给img的src时，记得加上时间戳或者保证url不重复，否则会被浏览器缓存，导致无法实时看到图片

转自：http://blog.csdn.net/mrliu20082009/article/details/7220203